Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $86.49   9.849%   $95.0084   $95.01   $95.00   $95.00  
  Purchase #2 $159.36   8.773%   $173.3407   $173.34   $173.35   $173.30  
  Purchase #3 $105.97   12.435%   $119.1474   $119.15   $119.15   $119.10  
  Purchase #4 $171.28   13.200%   $193.889   $193.89   $193.90   $193.90  
  Purchase #5 $208.86   8.333%   $226.2643   $226.26   $226.25   $226.30  
  Purchase #6 $75.29   11.533%   $83.9732   $83.97   $83.95   $84.00  
  Purchase #7 $148.57   8.515%   $161.2207   $161.22   $161.20   $161.20  
  7 purchase totals = $955.82       $1,052.8437   $1,052.84   $1,052.80   $1,052.80